Question on Output Music Hall MMF-5 / Sumiko Pre

Interesting...Thanks for the info! I appreciate it.

Chris

Your assumption is entirely correct. Warped records (and non-concentric punched records) can produce high amplitube subsonic distortion. It can damage drivers if someone were negligent, particularly with smaller mid/bass drivers and high power amps. Use common sense which means turning down teh volume, or get a phono unit with a subsonic filter, or even buy an in-line subsonic filter. This might be your least expensive solution at this point. If you know the input resistance of your pre-amp (usually 47K or 50K ohms), the filter can be as simple as a series capacitor. Without getting into the math, a .1uf cap in series with a 50K input resistor should yield about a 30 Hz corner frequency. (Now, this is a simple analysis without all possible parameter considerations, so no crucifixions please);^) Any value between .1uf (about 30Hz) and .15uf (about 20Hz) would work, but keep in mind that the higher cap value allows more low frequency to pass. Good luck.

Chris, the records that are causing the woofer flapping are probably warped. Warping creates subsonic signals that are transmitted to your cartridge to the preamp to amp and subsequently to the woofers. If you play your speakers loudly this could cause clipping and subsequent damage to your speakers. Excessive woofer cone excursions themselves could also be damaging. Your amp is being forced to amplify this signal.

I would suggest you try to unwarp those records, play them at low volume, get a phono preamp with a subsonic filter or get replacements. Good luck.